A trait that can provide the
Span of the complete contents of a syntax
This trait is automatically implemented for all types that implement
ToTokens from the
quote crate. It is sealed and cannot be implemented
outside of the Syn crate other than by implementing
See the module documentation for an example.
This trait is available if Syn is built with both the
Span covering the complete contents of this syntax tree
Span::call_site() if this node is empty.